1. Field of the Invention
The invention relates to a power converter providing a plurality of output voltages, and more particularly to an e-paper device which uses a power converter providing a plurality of output voltages.
2. Description of the Related Art
FIG. 1 shows a conventional boost power converter 1. The boost power converter 1 includes a power source 10, an inductor 11, a diode 12, a capacitor 13, resistors 14 and 15, a high power switch 16, and a controller 17 and provides an output voltage Vout10. The controller 17 generates a control signal CS10 to control the high power switch 16 to be turned on and off periodically. When the high power switch 16 is turned on according to the control signal CS10, the power source 10, the inductor 11, and the high power switch 16 form a loop. The inductor 11 stores energy by a current flowing through the loop. When the high power switch 16 is turned off according to the control signal CS10, the inductor 14 releases the stored energy. At this time, an inductor current is generated and flows to a load 18 through the diode 12. Accordingly, the output voltage Vout10 is generated. In the boost power converter 1, since the voltage across the two terminals of the high power switch 16 is vary high (being higher or equal to the output voltage Vout10) the high power switch 16 is turned off, switch loss of the high power switch 16 is high. Moreover, the high power switch 16 has to be a high voltage element to suffer the high voltage.
Recently, e-paper devices have been developed. Since power consumption of e-paper devices is very low, e-paper devices can be applied in mobile display devices using batteries. Power converters which drive e-paper devices are requested to have high voltage, low current, and high conversion efficiency characteristics and are requested to provide multiple output voltages. Thus, to achieve the objective of providing multi output voltages by the boost power converters, a power converter having a plurality of boost power converters 1, as shown in FIG. 2, has been developed for driving an e-paper device. Referring to FIG. 2, a power converter provides a plurality of output voltages Vout101˜Vout10m by using a plurality of boost power converters, wherein m is a positive integer. The boost power converters share one power source 10. Each boost power converter includes an inductor 11X, a diode 12X, a capacitor 13X, resistors 14X and 15X, a high power switch 16X, and a controller 17X with the similar structure to FIG. 1 and provides an output voltage Vout10X, wherein 1≦X≦m. However, the power converter having the boost power converters occupies a large area. Moreover, since the number of high power switches 161˜16m is increased with the number of the output voltages Vout101˜Vout10m, the total power loss due to the high power switches 161˜16m and the controllers 171˜17m is also increased, resulting in degradation of entire work efficiency.
Thus, it is desired to provide a power converter which provides a plurality of output voltages and has high work efficiency.